This invention relates to personal display devices and, more particularly, to controlling the display brightness based on the measured ambient light and lighting source characteristics.
The proliferation of compact portable display devices (e.g., portable MP3 players, portable video players, and media capable cellular telephones) has enabled users to interact with such compact portable display devices in environments that have widely varying ambient lighting conditions. Most devices include a display illumination system wherein the brightness level can be varied. Because these devices are often battery—powered and can be used while performing other activities, such as walking or running, it is desirable that the device automatically adjust its display brightness in response to surrounding ambient light conditions to conserve power and to avoid the need for a user to continually manipulate the display brightness manually.
One problem with existing display devices is that their ambient light sensors often detect light generated by their own display light sources or backlights which prevents the device from accurately measuring surrounding ambient light conditions. More particularly, existing display backlight controllers do not account for the emitted light from lighting elements after power to these elements is removed, which is caused by certain physical characteristics of the lighting elements. Accordingly, there is a need for accurately measuring varying ambient light conditions without interference from the device's own display light sources to enable enhanced backlight brightness control.
Another problem with existing portable display devices, such as cellular telephones, is that typical ambient light sensors can occupy space within the device's housing and require an external opening in the housing to enable ambient light detection. A light sensing opening in the housing may expose the device interior to the surrounding environment, increase manufacturing costs, or detract from an otherwise aesthetically pleasing design. Accordingly, there is a need for providing ambient light detection without requiring an additional opening in the device housing to support such detection.